Transient Substrate‐Induced Catalyst Formation in a Dynamic Molecular Network

Abstract

In biology enzyme concentrations are continuously regulated, yet for synthetic catalytic systems such regulatory mechanisms are underdeveloped. We now report how a substrate of a chemical reaction induces the formation of its own catalyst from a dynamic molecular network. After complete conversion of the substrate, the network disassembles the catalyst. These results open up new opportunities for controlling catalysis in synthetic chemical systems.

Dynamic Covalent Chemistry of Aldehyde Enamines: BiIII‐ and ScIII‐Catalysis of Amine–Enamine Exchange

“…Furthermore, the use of coordinating solvents, such as DMSO, decreased the catalytic effects substantially. Similar effects were also observed in Sc(OTf) 3 ‐catalyzed imine exchange . The fastest equilibrium formation of the model reaction was observed in CD 3 CN using Bi(OTf) 3 , where a forward rate of 16.0 m −1 h −1 was achieved.…”

“…The resulting reactions with bismuth triflate Bi(OTf) 3 (Table , entry 3) and scandium triflate Sc(OTf) 3 (Table , entry 4) displayed the highest rates (7.4–7.5 m −1 h −1 ) in attaining enamine equilibria, and >300 times rate enhancement compared to the uncatalyzed transenamination reaction (Table , entry 1). It can be noticed that this rate is generally >2 orders of magnitude higher than Sc(OTf) 3 ‐catalyzed imine exchange under identical conditions, thus supporting the use of catalyzed transenamination for generation of constitutional dynamic systems . Other Lewis‐acidic metal salts, including Zn(OTf) 2, Cu(OTf) 2 and AgOTf, also displayed catalytic effects, but to lower extents (Table , entries 5–7).…”

Temporal Control over Transient Chemical Systems using Structurally Diverse Chemical Fuels

“…First, the aggregation behaviour of C 16 TACN·Zn 2 + in the absence of fuels was monitored by the addition of increasing amountso ft he surfactant into an aqueous solution buffered at pH 7.0 containing the fluorescent apolarp robe 1,6-diphenyl-1,3,5-hexatriene( DPH, l ex = 355 nm, l em = 428 nm). DPH is solubilized by the hydrophobic environment of the aggregates and therefore an increasei nf luorescencei ntensity is observed once the critical aggregation concentration (CAC) is reached (Figure 5c).…”

“…[12] Although functional, these systems can be difficult to modulate and thus there is an eed for synthetic systems with greater flexibility. [13] Recently,e xamples of synthetic, dissipative processes driven by ac hemical fuel have been developed for the transient formation of physical structures such as gels, [14] vesicles, [15] and molecularc ages, [16] but also for the regulation of chemical processes, such as signal generation [17] and catalysis. [16b] Figure 1.…”

The Hydrolysis of the Anhydride of 2‐Cyano‐2‐phenylpropanoic Acid Triggers the Repeated Back and Forth Motions of an Acid–Base Operated Molecular Switch

“…[6] Ar emarkablee xample is has been reported by Leigh and co-workers, [6a] who synthetized a[ 2]-catenane in which one of the two macrocycles performs autonomous and unidirectionalc ircumrotations around the other, undert he influence of only one stimulus.F urthermore, autonomous molecular motionsi no ther systems such as 1) rotary motions aroundacovalentb ond, [7] 2) acid/base guided threading/dethreading in pseudorataxane systems, [8] 3) DNA-based molecular machines, [9] 4) molecular walkers, [10] have been achieved by means of chemical fuels. [11] Our contributionst ot he field is based on the Sauvage-type [2]-catenane 1,f or which the acid-base switching from the neutral state A to protonated states B'-B",a nd backa gain to state A is triggered by the decarboxylation of 1mol equiv of 2-cyano-2-phenylpropanoic acid 2 [5a] or its Cl, CH 3 ,a nd OCH 3 para-derivatives, [12] as shown in Scheme 1f or the reactionw ith the parent acid. The distinctive feature of the system is that the base required by back proton transfer from 1H + is generated in situ in the decarboxylation step B'!B".W hen the back protont ransfer is complete, the system is ready to perform another cycle after addition of another mol equiv of fuel.…”